Abstract: There are provided an optical disk and a manufacturing method thereof which can increase its recording capacity, e.g. to 15 GB or higher. This optical disk may comprises an optical disk substrate 3 in which successive pits corresponding to a recording signal are formed, a reflection film 4 formed in this optical disk substrate 3 on its surface that successive pits 2 are formed and a light transmissive layer 5 formed on this reflection film 4. When a recorded signal is read out, i.e. reproduced from the optical disk, a signal recorded as successive pits is read out by irradiating of short-wavelength laser light having a wavelength of 350 nm to 420 nm from the side of the light transmissive layer 5 formed on the surface of the optical disk.

Abstract: A stamper suppressed in surface roughness, uneven thickness, and deviation of circularity in inner circumference, a method of producing the same, an optical recording medium produced by molding using the stamper, and a method of producing the same, wherein a base member having a mirror polished main surface and comprising silicon or glass is formed with a resist film; the resist film is exposed by a focused electron beam, an ultraviolet ray laser, etc. and developed so as to form a resist film of a pattern corresponding to relief shapes; the mirror surface of the base member is processed to relief shapes (projecting regions and recessed regions) by dry etching etc. using the obtained resist film as a mask so as to obtain a stamper; the obtained stamper is used for injection molding to form a medium substrate; and an optical recording multilayer film and a protective layer are formed to thereby produce an optical recording medium.

Abstract: An optical disk having a recording capacity of about at least 15 GB and methods of making the same. The optical disk may include an optical disk substrate having successive pits formed into a first surface. The successive pits may correspond to a recording signal. The optical disk may further have a reflection film formed on the first surface of the optical disk substrate and in the successive pits and have a light transmissive layer formed on the reflection film. If a length of an effective pit length B of each pit of the plurality of successive pits is restricted to be not less than 80 nm and not greater than 250 nm, then a thickness T of the reflection film is restricted to be not greater than 20 nm and not less than 8 nm, and the thickness of the light transmissive layer is restricted to be not greater than 177 &mgr;m and not less than 10 &mgr;m.

Abstract: An optical disc having a light transmitting layer of a reduced uniform thickness. The optical disc has a transparent film bonded via a pressure-sensitive adhesive sheet or a dry photopolymer sheet on a substrate to serve as a light transmitting layer. The signal recording surface is formed on the substrate and/or the transparent film. The light transmitting layer may be constituted solely by a pressure-sensitive adhesive sheet or a dry photopolymer sheet. In the present optical disc, recording and/or reproduction is performed from the light transmitting layer with respect to the signal recording surface. The pressure-sensitive adhesive sheet or the dry photopolymer sheet is itself in a sheet form and is previously formed into a layer (sheet) of a pre-set thickness, in a manner different from the case in which a UV light curable resin is coated on a substrate.

Abstract: An optical disc and its manufacturing method in which humps may be prohibited from being formed on an outer rim area of the disc to assure optimum surface properties of a light transmitting layer of the disc to contribute to further increase in recording capacity. On a substrate 2 of an optical disc 1 are sequentially formed a recording portion 6 and a light transmitting layer 5. The light falls on the light transmitting layer 5 to record and/or reproduce information signals for a signal recording area 6a of the substrate 2. The radial distance D from the outermost rim of the substrate 2 to the signal recording area 6a is selected to be larger than the radial width L of a hump 5a formed on the outer rim of the light transmitting layer 5. The hump 5a has a height h from the surface of the light transmitting layer 5 not larger than 70 &mgr;m.

Abstract: An optical disc and its manufacturing method in which humps may be prohibited from being formed on an outer rim area of the disc to assure optimum surface properties of a light transmitting layer of the disc to contribute to further increase in recording capacity. On a substrate 2 of an optical disc 1 are sequentially formed a recording portion 6 and a light transmitting layer 5. The light falls on the light transmitting layer 5 to record and/or reproduce information signals for a signal recording area 6a of the substrate 2. The radial distance D from the outermost rim of the substrate 2 to the signal recording area 6a is selected to be larger than the radial width L of a hump 5a formed on the outer rim of the light transmitting layer 5. The hump 5a has a height h from the surface of the light transmitting layer 5 not larger than 70 &mgr;m.

Abstract: A multi-layer recording medium including a light-transmitting substrate, a first information recording layer formed on the substrate, an intermediate layer at least part of which is formed of a photo-curable resin film, and which is formed on the first information recording layer, a second information recording layer formed on a surface of the intermediate layer opposite to the surface facing the first information signal layer, and a protective layer formed on the second information signal layer. A method for producing such multi-layer recording medium is also disclosed.

Abstract: Such an optical recording medium is disclosed that includes at least one layer of an information layer (11) for which at least any of an optical recording or reproducing is performed with an optical parameter of N.A. (numerical aperture)/&lgr;(wavelength)≧1.2[&mgr;m−1], and in at least its information signal area, its focus error amount is equal to or less than ±&lgr;/(N.A.)2/8 in a band equal to or more than a focus servo cut-off frequency of an optical recording and reproducing apparatus which performs at least any of the optical recording or reproducing while within ±&lgr;/(N.A.)2/4 when only the reproduction is performed.

Abstract: A photoresist is applied onto a substrate, the photoresist-coated substrate is exposed to a laser beam of 300 nm or less in wavelength to form a latent image indicative of an information signal, and the photoresist on the substrate is developed to form a pit/groove pattern indicating the information signal. The photoresist has a mean value of 0.1 or less between extinction coefficients before and after the exposure to the laser beam.

Abstract: In an exposure device 20 for an optical disc master disc, the power density of light beam which is converged until the diffraction limit level by using a light source laser 1 of far ultraviolet radiation and an objective lens 7 having a numerical aperture of 0.85 or more is set to 4.upsilon..times.10.sup.2 W/cm.sup.2 or more (.upsilon.)[cm/sec] represents a linear velocity of recording), and a photoresist 8 on the master disc 9 of the optical disc is subjected to light exposure and heat treatment at the same time.

Abstract: An optical recording medium is provided which achieves a higher recording capacity. This optical recording medium includes a base formed of thermoplastic resin which has a thickness ranging from between approximately 0.3 to 1.2 nm, a guide groove formed on the base, at least a reflective film and a phase-change recording layer successively formed on the guide groove, arid a light transmissive layer having a thickness ranging from between approximately 3 to 177 .mu.m. In this optical recording medium, the unevenness .DELTA.t of the thickness of the light transmission layer is set within the range of:.DELTA.t.ltoreq..+-.5.26(.lambda./N.A..sup.4)(.mu.m)wherein N.A. represents a numerical aperture of an optical head device of the optical disk recording and/or reproducing apparatus and .lambda. represents the wavelength of laser light utilized by the optical disk recording and/or reproducing apparatus.

Abstract: An optical recording medium capable of recording and/or reproducing an information by using a laser beam, comprising: a support layer having an information signal-recording portion on one side surface thereof on which said laser beam is incident, and a transparent layer disposed over the support layer and having a thickness smaller than that of the support layer. In accordance with the present invention, there are further provided production method for optical or magneto-optical discs whereby a high density reproduction can be achieved.

Abstract: A multi-layer recording medium including a light-transmitting substrate, a first information recording layer formed on the substrate, an intermediate layer at least part of which is formed of a photo-curable resin film, and which is formed on the first information recording layer, a second information recording layer formed on a surface of the intermediate layer opposite to the surface facing the first information signal layer, and a protective layer formed on the second information signal layer. A method for producing such multi-layer recording medium is also disclosed.